c# - Intercept SOAP messages from and to a web service at the client

Question

I have a client that communicates with a web service. The class that I communicate with is a C# class that is generated through wsdl.exe. I now want to log all incoming and outgoing messages.

What I've done so far is to write a class that inherits from the automatically generated C# Class and I have overridden the GetReaderForMessage method. That way I can access the incoming message more or less like this:

protected override XmlReader GetReaderForMessage(SoapClientMessage message, int bufferSize)
{
    System.Xml.XmlReader aReader = base.GetReaderForMessage(message, bufferSize);
    System.Xml.XmlDocument doc = new System.Xml.XmlDocument();
    doc.Load(aReader);
    string content = doc.InnerXml.ToString();
    System.Xml.XmlReader aReader2 = System.Xml.XmlReader.Create(new System.IO.StringReader(content));

    return aReader2;
}

Obviously I'm not too happy with this solution, because basically I'm creating two xml readers. One to read the contents of the SOAP message and one to return to the method caller. Plus I can't really do the same with the GetWriterForMessage method.

But may be I'm just doing things too difficult to start with. Is it for instance possible to read the contents of the SoapClientMessage object directly? I've read some articles suggesting that I should use SoapExtensions here, but from what I can understand, that would only work if the 'client' that I am creating is itself a web service which in this case it is not.

Any suggestions?

Answer 1

You need to use "Add Service Reference" and not "Add Web Reference" feature to use this solution, it can be used if the service is ASMX or WCF. (You need to use .NET Framework 3.X to use this feature)

This article will help you to add the service reference to your C# project.

To intercept and XMLs of the request and the response, Implement these two classes:

public class InspectorBehavior : IEndpointBehavior
{
    public string LastRequestXML { 
        get
        {
            return myMessageInspector.LastRequestXML;
        }
    }

    public string LastResponseXML { 
        get
        {
            return myMessageInspector.LastResponseXML;
        }
    }


    private MyMessageInspector myMessageInspector = new MyMessageInspector();
    public void AddBindingParameters(ServiceEndpoint endpoint, System.ServiceModel.Channels.BindingParameterCollection bindingParameters)
    {

    }

    public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
    {

    }

    public void Validate(ServiceEndpoint endpoint)
    {

    }


    public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime)
    {
        clientRuntime.MessageInspectors.Add(myMessageInspector );
    }
}





public class MyMessageInspector : IClientMessageInspector
{
    public string LastRequestXML { get; private set; }
    public string LastResponseXML { get; private set; }
    public void AfterReceiveReply(ref System.ServiceModel.Channels.Message reply, object correlationState)
    {
        LastResponseXML = reply.ToString();
    }

    public object BeforeSendRequest(ref System.ServiceModel.Channels.Message request, System.ServiceModel.IClientChannel channel)
    {
        LastRequestXML = request.ToString();
        return request;
    }
}

Then, change the call code to:

MyTestServiceSoapClient client = new MyTestServiceSoapClient();
var requestInterceptor = new InspectorBehavior();
client.Endpoint.Behaviors.Add(requestInterceptor );
client.DoSomething("param1", "param2", "param3");
string requestXML = requestInterceptor.LastRequestXML;
string responseXML = requestInterceptor.LastResponseXML;

****EDIT**** This is not related with the serverside technology, you can use it with WCF, ASMX, PHP, ... web services, I have tested on: http://www.w3schools.com/webservices/tempconvert.asmx

And got the following XMLs:

requestXML=

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
  <s:Header>
    <Action s:mustUnderstand="1" xmlns="http://schemas.microsoft.com/ws/2005/05/addressing/none">http://tempuri.org/CelsiusToFahrenheit</Action>
  </s:Header>
  <s:Body xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <CelsiusToFahrenheit xmlns="http://tempuri.org/">
      <Celsius>50</Celsius>
    </CelsiusToFahrenheit>
  </s:Body>
</s:Envelope>

responseXML=

<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <s:Header xmlns:s="http://schemas.xmlsoap.org/soap/envelope/" />
  <soap:Body>
    <CelsiusToFahrenheitResponse xmlns="http://tempuri.org/">
      <CelsiusToFahrenheitResult>122</CelsiusToFahrenheitResult>
    </CelsiusToFahrenheitResponse>
  </soap:Body>
</soap:Envelope>

****EDIT 2****

"Add Web Reference" is not specialized for ASMX and is not an ASMX client-side technology, and "Add Service Reference"is not the WCF client-side technology, you can use both to add reference to ASMX, WCF, JSP-developed or PHP-developed, web service, you need your application to use .Net framework 3.5 to use "Add Service Reference".

This article mentions:

When using the Add Web Reference dialog box in Visual Studio, a client proxy is generated using WSDL information and is added to the Visual Studio project. This is usually used for ASMX services, but you can also use the Add Web Reference dialog box to create a client proxy for WCF services. However, you need to manually type the service URL, and the proxy that is generated uses XML serialization, which is the only type of serialization supported. To create client proxies for WCF services that support the data contract serializer, you can use the Svcutil.exe tool or use the Add Service Reference feature of the Visual Studio Development Tools for the .NET Framework 3.x.